The present invention relates to a pilot assembly of the type used in gas-fired appliances, particularly appliances such as furnaces and hot water heaters using natural gas as a source of fuel; and it also relates to a method manufacturing a gas pilot assembly of this type.
Gas pilots currently in use are not of the type previously used wherein the pilot burned continuously, referred to as a standing pilot. Rather, current technology employs ignition control circuits which inhibit the flow of gas to the pilot until a call for heat signal is received. At this time, a valve is opened to supply gas to the pilot, and an electrical signal of high frequency and voltage energizes a spark electrode strategically placed relative to gas emitted from the pilot tip for igniting the pilot flame. Fuel is then supplied to the main burner, and the flame is transferred from the gas pilot to the main burner. The gas pilot may also include a flame sensing electrode from which an electrical signal is generated in the presence of a flame. The flame sensing signal may either be a DC signal generated from rectification of an AC signal supplied to the flame sensing electrode, or it may be a conventional DC signal representative of reduced impedance in the presence of ionized gas.
Obviously, the dependability and reliability of a gas pilot are extremely important from the standpoint of safety. Extensive testing is performed with respect to the placement of a pilot relative to the main burner, and typically, a manufacturer's specifications on a pilot will vary from model to model for furnaces and other gas-fired appliances. From the viewpoint of a manufacturer of gas pilots, the large number of, and rather rigid specifications for, gas pilot assemblies create problems in manufacturing, inventory and so on, both for original equipment use and for replacement or retrofitting existing equipment with the new gas pilot.
As an example, a manufacturer may have hundreds of models and styles, when considering variations, for a gas pilot which performs basically the same functions.
The present invention, therefore, is intended to provide a gas pilot assembly which is universal in application in the sense that the same basic structural elements can be arranged and assembled during the manufacturing operation to meet the various specifications for different models and manufacturers of gas appliances. The invention is also directed to a method of manufacturing a universal gas pilot.
The pilot assembly includes a base in the form of an inverted cup having a cylindrical side wall. The cup is die formed from metal, and it holds an electrode subassembly as well as a tip subassembly which includes a pilot tip and orifice mechanically attached to the cup. The electrodes are held by a ceramic body, and the spark electrode is positioned relative to the tip by a locator member formed as an appendage on the tip.
The spark electrode is assembled to a clip member preferably formed from stainless steel which, upon brazing, will form a spring clip receptacle for receiving an end-plugged high tension wire. Glass preforms are placed on the cup surrounding the ceramic body, and additional preforms are placed on the electrodes above the ceramic body.
The assembly is then subjected to heat in a furnace, and this single step both brazes the metal and fuses the glass to provide a rigid assembly. One of the features of the invention is that both electrodes are rigidly secured in place relative to the cup, the pilot tip, and their associated connecting wires so that electrical shorts or open circuits become highly unlikely even though the assembly may be subjected to severe conditions.
Following the heating step, a mounting bracket having a vertically elongated mounting plate and a laterally extending connecting flange is then assembled to the side wall of the cup base and spot-welded to it, and the locator member is cut off the tip to provide the desired spark gap.
In the illustrated embodiment, the mounting plate and the connecting flange of the mounting bracket are disposed at right angles and spaced such that the connecting flange can be secured to the cylindrical side wall of the cup base at any rotational angle of the cup. Further, the axis of the cylindrical side wall of the cup can be angularly disposed, within limits, relative to the plane of the mounting plate of the mounting bracket. Still further, the mounting bracket may be assembled to the cup in either of two vertical orientations so that the mounting plate may extend above the cup or beneath it, and it may be continuously adjusted axially relative to the cup in either of these positions. There is thus provided a very broad range of orientations of the pilot relative to the mounting bracket so as to meet a large number of specifications for different manufacturers relative to placement of the pilot assembly in an appliance by means of the cooperative relationship between the structure of the mounting bracket and the structure of the pilot assembly.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.